The above configuration specifies a theme located under the "themes/basic" directory of the Web folder
that contains the entry script of the application. If your theme is designed to handle modules,
you may configure the $pathMap property like described above.

The mapping between view directories and their corresponding themed versions.
This property is used by applyTo() when a view is trying to apply the theme.
Path aliases can be used when specifying directories.
If this property is empty or not set, a mapping yii\base\Application::$basePath to $basePath will be used.